Temporal and spatial changes of fish biomass during the warm season in the Russian part of the elittoral of the Sea of Japan

Abstract

Total biomass of fish in the Russian elittoral zone of the Sea of Japan during the warm period, according to surveys performed from 1983 to 2006, was 475.6 thousand tons, or 8.8 t/km 2 . Relatively high val ues of specific biomass were recorded in the 1980s, and the maximum value (29.2 t/km 2 ) was recorded in 1986, reflecting the cooccurrence of dramatic surges in the Alaska pollock (Theragra chalcogramma) and the Pacific herring (Clupea pallasii). In the 1990s, the total biomass of fishes decreased by an order of magnitude, and over almost the entire decade remained approximately at the same level (4.5-6.7 t/km 2 ); after 2001, this parameter never reached higher values than 4.4 t/km 2 . The average annual density of fish biomass varied in different areas from 5.8 t/km 2 (northern Strait of Tartary) to 13.3 t/km 2 (southern Primorskii krai). The prin cipal factor determining the value of specific fish biomass in particular areas is the level of the Alaska pollock's resources. In the elittoral, the highest concentration of the absolute majority of dominant and subdominant species are confined to the range of depths from 50 to 100 m.